Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$8.58	4.556%	$8.9709	$8.97	$8.95	$9.00
Purchase #2	$63.36	5.778%	$67.0209	$67.02	$67.00	$67.00
Purchase #3	$153.28	12.127%	$171.8683	$171.87	$171.85	$171.90
Purchase #4	$171.26	10.537%	$189.3057	$189.31	$189.30	$189.30
Purchase #5	$53.57	11.863%	$59.925	$59.93	$59.95	$59.90
Purchase #6	$89.55	10.430%	$98.8901	$98.89	$98.90	$98.90
Purchase #7	$142.42	10.137%	$156.8571	$156.86	$156.85	$156.90
7 purchase totals =	$682.02		$752.8380	$752.85	$752.80	$752.90